Proteolysis of mammary secretion proteins during involution of bovine mammary gland
Aslam, Mueen
This item is only available for download by members of the University of Illinois community. Students, faculty, and staff at the U of I may log in with your NetID and password to view the item. If you are trying to access an Illinois-restricted dissertation or thesis, you can request a copy through your library's Inter-Library Loan office or purchase a copy directly from ProQuest.
Permalink
https://hdl.handle.net/2142/21820
Description
Title
Proteolysis of mammary secretion proteins during involution of bovine mammary gland
Author(s)
Aslam, Mueen
Issue Date
1996
Doctoral Committee Chair(s)
Hurley, Walter L.
Department of Study
Animal Sciences
Discipline
Animal Sciences
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Agriculture, Animal Culture and Nutrition
Chemistry, Biochemistry
Language
eng
Abstract
In cattle, during the early dry period the mammary gland undergoes a process of involution. The profile of mammary secretion proteins changes throughout the dry period. Increased proteolytic activity and breakdown fragments of milk proteins contribute to the composition of mammary secretions during dry period. The objectives of this study were (a) to determine the two-dimensional protein profile of mammary secretion proteins and peptides during involution, (b) to measure plasmin, plasminogen and plasminogen activator activity in mammary secretions collected during involution, and (c) to identify and characterize milk protein derived-peptides in mammary secretions during involution. Proteins in mammary gland secretions, collected from Holstein cows during the dry period, were analyzed by preparative isoelectric focusing, followed by SDS-PAGE. Protein profiles changed throughout the dry period. Intact casein bands were present throughout the dry period, but in reduced proportions from d 7 after drying-off through d 7 prepartum. Breakdown fragments of casein were particularly apparent in secretions from d 7 to 21 of the dry period. A fragment of $\beta$-CN ($\sim$13 kDa) was identified in secretions collected on d-1 prior to dry-off through d 21 of the dry period. Lactoferrin was found in all fractions after isoelectric focusing, but specific degradation products of lactoferrin were apparent only at certain times during the dry periods. Plasmin, plasminogen and plasminogen activator activities were significantly higher ($P <$ 0.05) on d 7, 14 and 21 of involution compared to d 7 postcalving. Immunoblot analysis showed that a number of peptides observed on d 7, 14 and 21 of involution were generated from $\alpha$s-casein, $\beta$-casein, $\kappa$-casein, or lactoferrin. Four peptides with apparent molecular weights ranging from 8 to 13 kDa were identified as $\beta$-casein fragments by amino acid sequence analysis. Mass spectrometric analysis of mammary secretions shows several peptides ranging from 0.8 to 12 kDa on d 7, 14, and 21 of involution. Mass spectrometric analysis of lactoferrin fractions collected from heparin-agarose chromatography showed at least four peaks of about 16, 20, 56, and 63 kDa. Results from this study show that $\beta$-casein-derived peptides are produced by the plasmin cleavage. These and other peptides generated in mammary secretions may have functional role in the involuting mammary gland.
Use this login method if you
don't
have an
@illinois.edu
email address.
(Oops, I do have one)
IDEALS migrated to a new platform on June 23, 2022. If you created
your account prior to this date, you will have to reset your password
using the forgot-password link below.
